1856.] on Aluminium, %\\ 



The speaker here adverted to the enormous difference which 

 exists, not only between the alkaline metalu and those of the former 

 groups, but also between their respective ores. Neither the ore of 

 potassium, nor (in Davy's time) the ore of sodium, could be ob- 

 tained directly from the soil through which its weak solution is 

 diffused ; it had to be sought in the tissues of plants, which 

 absorbed it from the ground. When obtained and concentrated, 

 this substance is fusible, soluble, corrosive, and possessed of im- 

 mense chemical power. The metal derived from this strange ore, 

 though possessing lustre, ductility, malleability, power of conducting 

 heat and electricity, differs in every other respect from every 

 metal yet known. Its specific gravity is less than that of water, and 

 its affinity for oxygen so great as to necessitate the invention of 

 hitherto unknown expedients to prevent the metal from returning 

 to its state of oxide as soon as it was separated from it. 



Davy seems to have accounted for the results he produced by 

 assuming that the poles of the battery acted as centres of force ; that 

 the potassium being repelled by one pole was attracted by the other, 

 like any light substance placed between two surfaces charged with 

 opposite Franklinic electricity. Faraday* has taught that the whole 

 of the subjected body is pervaded by this decomposing force as an 

 axis of power, so that a particle in the middle is as much affected aa 

 a particle at the extremities of it ; that, in order to be under the 

 influence of this force, the body must be fluid, and a conductor of 

 electricity, and that its elements must exist in a simple relation to 

 each other, and that the proportional amount in which these elemen- 

 tary substances, separated by electrical decomposition, are severally 

 ejected at the electrodes (electrical outlets), corresponds exactly 

 with that of their combining numbers. In accordance with these 

 views the voltaic pile may be regarded as a flameless furnace, whose 

 reducing power is conveyed by the conducting wires to the spot 

 where the ore is subjected to its influence. By these means not 

 only the alkalies but the alkaline earths were decomposed, and their 

 respective metals, barium, calcium, strontium, and lithiumf obtained. 

 But aluminium cannot be separated from alumina, its sesquioxide, 

 by electrolysis. The metal does not in this case (as in those of 

 potass, lime, strontia, &c.,) combine with oxygen or any like body 

 in single proportionals ; and alumina, its only known oxide, is also 

 infusible, except before the blow-pipe. 



But although the voltaic battery be unable to separate alumi- 



* Experimental Researches in Electricity, Fifth Series. A perspicuous 

 summary of the principles of this philosophy will be found in the History of the 

 Inductive Sciences, ed. 1837, Vol. iii. p. 163, &c. ; and Grove's Correlation of 

 the Physical Forces, ed. 1S55, p. 172, &c. 



t M. Warren De la Rue exhibited specimens of lithium produced from the 

 fused chloride by means of voltaic electricity. The negative pole was an 

 iron wire ; the positive, a piece of coke. Lithium is the lightest substance 

 known. 



